Conventional methods of infrared spectroscopy utilize either a small throughput (IR flux) optical element for dispersion, followed by a detector or a detector array, or a large throughput, scanning interferometer followed by a detector. In application of the first technique, the spectrum is accessed directly in the wavelength and frequency domain, while in the second the spectrum is measured in the time domain and then transformed (typically using Fourier algorithms) by a post-measurement calculation to the wavenumber domain.
As is known to those skilled in the art, the first method is relatively simple to implement, but is also of relatively low sensitivity due to the small amount of light throughput involved; in addition, long scanning times are required if the spectral range encompassed is substantial, and the instrument itself must be fairly large if good resolution is to be had. On the other hand, methods using scanning interferometers find wide application in Fourier-transform infrared (FT-IR) spectroscopy and in other specialized applications (e.g., piezoelectric scanning Fabry-Perot interferometers), but the instruments employed can be very complex and expensive, and can lack durability, largely because of their requirement for high-precision moving optics.
Additional limitations, common to both spectroscopy methods described, are related to the materials presently available for IR detectors. Current detector technology is based either upon photoelectric semiconductor materials, which are of a narrow band character, or upon broad-band but low-sensitivity photo-thermal materials, which are of slow response; both kinds of materials are, in addition, difficult to fabricate into satisfactory arrays.